With the advent of greater emphasis on physical fitness and exercise and with more and more participation by older individuals in sports, there has been a dramatic rise in traumatic injuries to the shoulder. Such injury and subsequent surgery often results in a decrease in the range of shoulder motion, including shoulder rotation. Decrease in range of shoulder motion can also be caused by progressive diseases such as tendinitis, bursitis, arthritis and adhesive capsulitis, commonly known as "frozen shoulder."
Also, within the last 15 years, advances in shoulder surgery have resulted in shorter convalescent periods and hospital stays. Shoulder surgery on an outpatient basis, such as arthroscopic surgery, is commonly practiced. Accordingly, there is now an increased need for outpatient physical therapy. It is also desirable for the patient to engage in exercise therapy in the home to increase the frequency of exercise resulting in faster shoulder rehabilitation while at the same time reducing medical costs.
It has been determined in recent years that after shoulder surgery regular physical therapy enhances recovery and shortens the time for recovery, especially for surgery involving shoulder repair, such as the repair of rotator cuff tears and decompression. It has been found that after an initial period of healing, regular stretching of the muscles by rotation of the shoulder increases both the flexibility and range of motion for the shoulder.
To avoid overtaxing and injury to the shoulder muscles after surgery gradual assistive, passive exercises such as shoulder rotation and stretching are recommended to be used rather than active exercise. In a passive exercise, the shoulder is stretched and rotated in a manner not requiring any force or exertion by the shoulder muscles themselves or through use of the arm. In active exercise, the shoulder muscles of the shoulder being exercised supply the force needed to cause the stretch or rotation.
In performing shoulder stretching and rotation exercises it has been found to be difficult for either the exerciser or an assistant to apply a steady, safe load to the shoulder. Moreover, it is difficult to accurately apply the same directional force for both internal rotation and external rotation of the shoulder each time the shoulder-related muscles are to be stretched. Thus, the extent to which the shoulder-related muscles are stretched can vary considerably from day to day and from time to time using exercise without an assisting apparatus.
It is known that after a muscle is stretched to or near its maximum level for a period of time, if maximum contraction of the muscle is made and the muscle has been allowed to relax, a proprioceptive neuromuscular facilitation phenomenon occurs whereby a dip in the muscle stretch reflex occurs so that the muscle can be stretched somewhat further. Thus, by increasing the range of stretching and rotation of the shoulder eventually to its full range of motion, the range of shoulder motion upon rehabilitation can be increased.
In the therapeutic and rehabilitative stretching and rotation of the shoulder described herein, it is desirable that the forearm remain in a fixed 90.degree. angle with reference to the humerus of the upper arm, with the upper arm alongside or parallel to the body. The forearm may then be moved in a 90.degree. arc to the left or the right, which cumulatively provides for a 180.degree. stretch and rotation of the shoulder. This movement may occur while the patient is standing, but it is preferable for the patient to be lying on his or her back in a supine position. In addition, it is desirable that stretching and rotation of the shoulder be done in a passive state, i.e., without any tension or force on the shoulder other than the force required to move the forearm. The supine position removes the weight of the arm from the shoulder.
Prior to this invention, there were no devices known in physical therapy that could provide passive motion for both internal and external rotation and that were self-assistively operated. However, continuous passive movement machines for stretching and rotating the shoulder through flexion and extension of the arm are known in the art. Examples of such machines are the Cyvex Isokinetic Machine, the Biodex Isokinetic Machine, the Kincon Isokinetic Machine and the Continuous Passive Movement Machine (collectively referred to as "CPMs"). CPMs generally operate using motors, and thus do not provide for a release of force should stiffness or muscle soreness result in discomfort or pain after a certain degree of motion or stretch is reached. Further, CPMs are known only to provide for flexion and extension of the arm and shoulder and not internal and external rotation and stretching, particularly in the preferred supine position. Although CPMs are designed for the patient to be either in a vertical or supine position, both types generally drag the arm up and down. Because of the high costs involved, CPMs have to be used in conjunction with professional care such as that of a physical therapist in a clinic. Few persons can afford a CPM for use in the home. Further, CPMs are not portable.